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Levulinic acid(LA) is produced through acid-catalyzed hydrolysis and dehydration of lignocellulosic biomass. It is a key platform chemical used as an intermediate in various industries including biofuels, cosmetics, pharmaceuticals, and polymers. Traditional LA production uses chemical conversion, which requires high temperatures and pressures, strong acids, and produces undesirable side reactions, repolymerization products, and waste problems Therefore, we designed an integrated process to produce LA from glucose through metabolic engineering of Pseudomonas putida KT2440. As a metabolic engineering strategy, codon optimized phospho-2-dehydro-3-deoxyheptonate aldolase (AroG), 3-dehydroshikimate dehydratase (AsbF), and acetoacetate decarboxylase (Adc) were introduced to express genes of the shikimate and β-ketoadipic acid pathways, and the 3-oxoadipate CoA-transferase (pcaIJ) gene was deleted to prevent loss of biosynthetic intermediates. To increase the accumulation of the produced LA, the lva operon encoding levulinyl-CoA synthetase (LvaE) was deleted resulting in the high LA-producing strain P. putida HP203. Culture conditions such as medium, temperature, glucose concentration, and nitrogen source were optimized, and under optimal conditions, P. putida HP203 strain biosynthesized 36.3 mM (4.2 g/L) LA from glucose in a fed-batch fermentation system. When lignocellulosic biomass hydrolysate was used as the substrate, this strain produced 7.31 mM of LA. This is the first report of microbial production of LA from glucose by P. putida. This study suggests the possibility of manipulating biosynthetic pathway to produce biological products from glucose for various applications. • A strategy to produce levulinic acid from glucose was developed in P. putida KT2440. • Introducing aroG , asbF , and adc genes enabled levulinic acid production from glucose. • Deleting the pcaIJ and lvaE genes increased levulinic acid production in P. putida. • A levulinic acid yield of 36.3 mM (4.2 g/L) was achieved in fed-batch fermentation. • This is the first report of microbial levulinic acid production from glucose. [ABSTRACT FROM AUTHOR]

Levulinic acid, which can be obtained from biomass, has sparked great interest as a biologically-based chemical building block with wide versatility and potential. Its esterification with alcohols of different chain lengths is a promising valorization process for obtaining esters with various applications in the areas of biofuels/biolubricants, food and cosmetics, among others. In this work, the enzymatic esterification of levulinic acid and 1-octanol using a biocatalyst derived from Araujia sericifera latex was studied in systems with and without solvent. The influence of the molar ratio between alcohol and acid (ranging from 2:1–1:9), the biocatalyst loading (between 7.5 % and 17.5 % relative to the acid), the volume of n -heptane used as reaction solvent (from 0 to 4 ml), and the reaction time (6 hours) were investigated. The activity and stability of the biocatalyst in successive uses were also analyzed. A conversion of 49 % was achieved when the reaction was carried out in a solvent-free system, using an alcohol/acid molar ratio of 1:7 and after 5 h of reaction. On the other hand, the conversion was 65.1 % when the reaction was conducted in a system containing 1 ml of n -heptane as solvent, an alcohol/acid molar ratio of 1:8, and 5 h of reaction. In both cases, a temperature as low as 30 °C and an agitation speed of 300 RPM were used. • Enzymatic route for levulinic acid esterification using biocatalyst. • Araujia sericifera latex-derived biocatalyst demonstrates high activity. • Achieved 65.1 % conversion of levulinic acid in the synthesis of octyl levulinate. • Solvent-free and n-heptane solvent systems investigated. • Studied reaction parameters for optimal conversion. [ABSTRACT FROM AUTHOR]

Levulinic acid is an important chemical intermediate, which has many applications in organic synthesis, industry, agriculture, and medicine. In this word, three kinds of heteropoly acid based ionic liquids ([IMPS]H2PW12O40、[PyPS] H2PW12O40 [TEAPS] H2PW12O40) were used to catalyze the one‐pot conversion of cellulose to levulinic acid. [IMPS]H2PW12O40 has the highest catalytic activity due to its strong Hammett acidity (H0). In addition, the effect of biphasic solvent systems on the conversion of cellulose to levulinic acid was also studied. The results showed that the GVL/H2O system could effectively promote the conversion of cellulose and increase the yield of levulinic acid. The yield of levulinic acid could reach 52.6% and the conversion rate of cellulose was 91.2% at 180 °C for 180 min under the GVL/H2O volume ratio of 1:1 with [IMPS]H2PW12O40 as a catalyst at 1 Mpa N2 and cellulose as raw material. And [IMPS]H2PW12O40 can be recycled up to five times without significant performance loss. This study provides a promising method for efficiently converting cellulose and other biomass resources to levulinic acid extraction. [ABSTRACT FROM AUTHOR]

The purple Cameroon grass crop (P. purpureum cv. Morado) presents significant potential as a source of raw materials and renewable energy; it has rapid growth, high yield, and low fertilizer demand. During the conversion of lignocellulosic biomass, hemicellulose and cellulose can first be hydrolyzed into five and six-carbon sugars, and then the sugars are converted into furfural and levulinic acid (LA) respectively. In this work, the furfural and levunilic acid production was evaluated in a two-stage catalytic process with a tin catalyst supported on a sulfonated activated carbon. In the first stage, a furfural yield of 23.28% at 170 °C for 3 h. In the second stage, the effect of process temperature and time on LA production's yield and energy demand was evaluated; LA yield of 28.17% was obtained with an energy demand of 0.12 kWh/gLA at 180.47 °C for 1.78 h. These results demonstrate the possibility of obtaining furfural from Cameroon grass. [ABSTRACT FROM AUTHOR]

Levulinic acid (LA) was produced from oil palm empty fruit bunch (OPEFB) pretreated in two different ways: (1) a two-step treatment with peracetic acid (PA) and alkaline peroxide (AP); and (2) an ammonia soak pretreatment. The pretreated material was subjected to acid hydrolysis (5% w/v sulfuric acid, 125 °C to 175 °C, 120 min) to produce LA. Compared to the ammonia treatment, the two-step PA–AP pretreatment was better in removing lignin from OPEFB, and resulted in a higher LA yield based on the mass of the pretreated OPEFB. On a mass basis, the LA yield was 31.1% on pretreated OPEFB, that had been pretreated using the PA–AP process, but only 16.7% from the biomass treated using the ammonia process. The kinetics of acid-catalyzed production of LA from the pretreated OPEFB were investigated to develop a mathematical model for predicting the conversion of cellulose to the intermediates (glucose, 5-hydroxymethylfurfural), and the final product, LA. The hydrolysis of cellulose to glucose was found to be the rate-controlling step in acid-catalyzed production of LA, confirming the importance of the delignification pretreatment in making cellulose more amenable to hydrolysis. During the two-stage acid hydrolysis, the reaction at 175 °C for 15 min in the first stage, followed by 125 °C for 105 min in the second stage, resulted in LA molar yield (based on cellulose) of ∼40%. This was comparable to the yield obtained if both steps were performed at 150 °C for a total of 120 min. [ABSTRACT FROM AUTHOR]

Various heterogeneous bimetallic Ru, Rh, Pd and/or Cu‐containing catalysts, based on dendrimer‐silica mesoporous hybrid supports, are successfully synthesized, using co‐complexation method, and characterized by transmission electron microscopy and X‐ray photoelectron spectroscopy. The catalysts obtained are examined in the aqueous hydrogenation of levulinic acid and its esters to γ‐valerolactone. The catalyst activity and selectivity on γ‐valerolactone are strongly dependent on the nature and ratio of metal used, and PdRu bimetallic catalysts are found to be the most effective. Quantitative or near to quantitative yields of γ‐valerolactone can be achieved for all PdRu catalysts and substrates tested within 2 hours, with maximum TOF value of 4500 h−1. Such high efficiency is provided by especial nanoparticle structure, consisted of Pd core and RuPd shell, and synergistic effect between Ru and Pd in alloy. [ABSTRACT FROM AUTHOR]

Lignocellulosic agricultural wastes are a potential feedstock for the synthesis of fuels and chemicals due to their low environmental cost, environmental friendliness, sustainability, and abundance. Therefore, corn byproducts are regarded as a valuable bioresource with multiple applications. In this study, platform chemicals, including levulinic acid (LA), formic acid (FA), and furfural (FF), were synthesized from corn husk by hydrothermal conversion using an acidic catalyst and a statistical Box-Behnken method. When selecting catalysts with MSA, H3PO4, H2SO4, HCl, and HNO3, the highest LA yield was obtained with methanesulfonic acid (MSA). At 170 °C, 12.5% biomass, 0.75 M MSA, and 40 min, the statistical optimization of corn husk conversion produced a yield of 18.0wt% LA based on biomass weight (57.75% based on carbohydrate content). Concurrently, an FA yield of 9.23wt% was achieved. At 170 °C, 5% biomass, 0.20 M MSA, and 15 min; however, a yield of 11.4wt% FF based on biomass weight (36.57% based on carbohydrate content) was obtained. LA and FA productions with combined severity did not fit the nonlinear sigmoidal model well. Nonetheless, the production of FF well-fitted the sigmoidal model with a high regression value. In corn waste biorefineries, the utilization of corn husk as bioresources and MSA as the catalyst for the synthesis of levulinic acid is well-understood. [ABSTRACT FROM AUTHOR]

Levulinic acid (LA) is one of the top bio‐based platform molecules that can be converted into many valuable chemicals. Herein, we report the sustainable synthesis of LA acid from various sugars using heteropolyacid catalysts. By using a Box–Behnken design of experiment, both LA yield (up to 69 mol%) and complete suppression of parasitic humin formation could be achieved within a 5 h reaction time at 140°C using fructose as a substrate. The effects of various reaction parameters like temperature, sugar concentration, addition of organic co‐solvent and reaction time on LA yield and humin formation were examined in a three‐dimensional space. Moreover, the results could be successfully transferred to other sugars like glucose or cellobiose, paving the way for an atom‐efficient and sustainable LA synthesis process. [ABSTRACT FROM AUTHOR]

This paper presents the results of the use of MFI zeolite as a catalyst modified with tin and iron. Sn‐MFI and Fe‐MFI catalysts were obtained by ion exchange under hydrothermal conditions with and without ammonium exchange. Catalytic materials were characterized with the use of analytical techniques such as X‐ray diffraction (XRD), Brunauer–Emmett–Teller method (BET), diffuse reflectance spectroscopy in the ultraviolet‐visible range (DRS UV–visible), hydrogen temperature programmed reduction (H2‐TPR), or Fourier transform infrared (FTIR) spectroscopy. The one‐pot catalytic conversion of fructose was performed at 220 °C for 1–5 h. Based on the results, the influence of time and material selection on the products obtained can be seen. Lactic acid (LAC) was obtained with a yield of 68.7% (after 2 h) and levulinic acid (LA) with a yield of 70.9% (after 5 h) with the participation of MFI. In turn, formic acid with a yield of 28.5% (after 5 h) was obtained with the participation of Fe‐MFI. [ABSTRACT FROM AUTHOR]

This work developed an efficient route to produce fuel bioadditive alkyl levulinates. Special attention was paid to butyl levulinate, which is a bioadditive with an adequate carbon chain size to be blended with liquid fuels such as diesel or gasoline. In this process, levulinic acid was esterified with butyl alcohol using cheap and commercially affordable metal nitrates as catalysts, producing bioadditives at more competitive costs. Iron (III) nitrate was the most active and selective catalyst toward butyl levulinate among the salts evaluated. In solvent-free conditions, with a low molar ratio and catalyst load (1:6 acid to alcohol, 3 mol% of Fe (NO3)3), conversion and selectivity greater than 90% after an 8 h reaction was achieved. A comparison of the iron (III) nitrate with other metal salts demonstrated that its superior performance can be assigned to the highest Lewis acidity of Fe3+ cations. Measurements of pH allow the conclusion that a cation with high Lewis acidity led to a greater H+ release, which results in a higher conversion. Butyl levulinate and pseudobuty levulinate were always the primary and secondary products, respectively. The consecutive character of reactions between butyl alcohol and levulinic acid (formation of the pseudobutyl levulinate and its conversion to butyl levulinate) was verified by assessing the reactions at different temperatures and conversion rates. A variation in Fe(NO3)3 catalyst load impacted the conversion much more than reaction selectivity. The same effect was verified when the reactions were carried out at different temperatures. The reactivity of alcohols with different structures depended more on steric hindrance on the hydroxyl group than the size of the carbon chain. A positive aspect of this work is the use of a commercial iron nitrate salt as the catalyst, which has advantages over traditional mineral acids such as sulfuric and hydrochloric acids. This solid catalyst is not corrosive and avoids neutralization steps after reactions, minimizing the generation of residues and effluents. [ABSTRACT FROM AUTHOR]

Levulinic acid (LA) is a significant building block in industry. It can be produced by the hydrolysis of lignocellulosic feedstocks and needs to be separated from the aqueous production medium. This study focuses on evaluating fly ash, a waste byproduct from a sugar factory, for use in the adsorption of LA from aqueous media. The sugar beet processing fly ash (SBFA) was characterized using XRD, FTIR, SEM, and N2 adsorption-desorption analysis. The data fit the pseudo-second-order kinetic model, with good agreement between the experimentally measured (454.55 mg g–1) and calculated (452.40 mg g–1) adsorption capacities. It was observed that the efficiency slightly decreased with increasing temperature, with the effect more pronounced at lower concentrations. Calculated thermodynamic parameters demonstrated that the process was exergonic and exothermic. The capacity of LA adsorption reduced with SBFA dose while enhanced with acid concentration, achieving a maximum of 464 mg LA/g SBFA, higher than values previously achieved with other adsorbents. The Langmuir isotherm model fit well with equilibrium data. Complete recovery of LA was achieved using 0.2 M NaOH, and SBFA could be reused with high efficiency for five consecutive cycles.

Abstract This paper focuses on the reactive extraction of levulinic acid (LA) from aqueous solution by reactive extraction. This goal is achieved using eugenol, a green alternative in the industry, as a solvent in the liquid-liquid equilibrium (LLE) measurements for the ternary system of LA + Eugenol + H2O and quaternary systems of LA + Eugenol/ Methanol (MeOH) + H2O + Tri-n-octylamine (TOA) at T = 293.15 K. Additionally, the distribution coefficients (K D) were calculated for LA using the two diluents. Also, the ability of different diluents with TOA, in the extraction of LA were compared. The distribution coefficient of eugenol with TOA (K D = 9.44) is compared with other organic diluents which indicated that eugenol is a suitable option. MeOH, being the shortest chain alcohol, also turned out to be a diluent that could be utilized for extraction of LA with TOA. Furthermore, the Non-Random Two-Liquid (NRTL) excess Gibbs energy model was applied to correlate the measured phase equilibria. The obtained parameters were further validated using a decanter model.

Among the different polyoxometalate compounds, Keggin heteropolyacids have been extensively used as catalysts in several acid-catalyzed reactions, due to their strong strength of Bronsted acidity. These metal–oxygen clusters have a highly versatile structure that allows their conversion to derivatives, which are catalysts that are much more efficient than their precursors, with a greater catalytic activity in a plethora of reactions of industrial interest. Particularly, due to the inevitable exhaustion of fossil sources, reactions to valorize biomass have attracted significant attention, since it is a precious renewable raw material that can provide fine chemicals or fuels, minimizing our dependence on petroproducts. Biorefinery processes can produce platform molecules to achieve this goal. In this review, the recent advances achieved in the development of routes to converting biomass feedstocks to levulinic acid and furfural, which are valuable ingredients in biorefinery processes, using Keggin heteropolyacid catalysts were assessed.

γ-valerolactone (GVL), derived from biomass, is a crucial platform compound for biofuel synthesis and various industrial applications. Current methods for synthesizing GVL involve expensive catalysts and high-pressure hydrogen, prompting the search for greener alternatives. This study focuses on a novel zirconium phosphate (ZrP)-pillared zeolite MCM-36 derivative catalyst for converting levulinic acid (LA) to GVL using alcohol as a hydrogen source. The incorporation of ZrP significantly contributes to mesoporosity and greatly enhances the acidity of the catalysts. Additionally, we employed 31P MAS NMR to comprehensively investigate the influence of phosphorus species on both the acidity and the catalytic conversion of LA to GVL. By adjusting the Zr-to-P ratios, we synthesized catalysts with enhanced acidity, achieving high conversion of LA and selectivity for GVL. The catalyst exhibited high recyclability, showing only minor deactivation over the course of five cycles. Furthermore, the catalyst was successfully applied to the one-pot conversion of furfural to GVL, showcasing its versatility in biomass conversion. This study highlights the potential of the MCM-ZrP1 catalyst for sustainable biomass conversion and offers insights for future research in renewable energy technologies. [ABSTRACT FROM AUTHOR]

This paper reports a new sustainable protocol for the microwave‐assisted catalytic conversion of levulinic acid into N‐substituted pyrrolidones over tailor‐made mono (Pd, Au) or bimetallic (PdAu) catalysts supported on either highly mesoporous silica (HMS) or titania‐doped HMS, exploiting the advantages of dielectric heating. MW‐assisted reductive aminations of levulinic acid with several amines were first optimized in batch mode under hydrogen pressure (5 bar) in solvent‐free conditions. Good‐to‐excellent yields were recorded at 150 °C in 90 min over the PdTiHMS and PdAuTiHMS, that proved recyclable and almost completely stable after six reaction cycles. Aiming to scale‐up this protocol, a MW‐assisted flow reactor was used in combination with different green solvents. Cyclopentyl methyl ether (CPME) provided a 99 % yield of N‐(4‐methoxyphenyl) pyrrolidin‐2‐one at 150 °C over PdTiHMS. The described MW‐assisted flow synthesis proves to be a safe procedure suitable for further industrial applications, while averting the use of toxic organic solvents. [ABSTRACT FROM AUTHOR]

A series of activated carbons (YMBC) obtained from yerba mate twig residue (YMT) were prepared by chemical (H3PO4) and thermal activation. Five materials were synthesized, varying the carbonization temperature (400–600 °C under N2 atmosphere) and H3PO4:YMT ratio (60–80 wt%). They were physicochemically and texturally characterized by SEM-EDX, BET, FT-IR, and 31P MAS-NMR. Potentiometric titration with the n-butylamine technique was used to evaluate their acidic properties. The materials exhibited a high specific surface area (572 m2 g−1 < SBET < 1031 m2 g−1) and mesoporosity (67% < Smeso/SBET < 93%). The results showed that the acid strength and the number of acid sites increased with the H3PO4:YMT ratio and decreased with the calcination temperature increment. The FT-IR and 31P characterization revealed the presence of Hn+2PnO3n+1 species firmly (via P-O-C linkages) and loosely attached (by electrostatic interaction). The latter were successfully removed by refluxing the material in water or n-propanol. The optimal reaction conditions were applied to the synthesis of other levulinic acid esters using YMBC-500-70NP as a catalyst. Furthermore, the effective separation of the product combined with the use of a recyclable catalyst resulted in a clean and environmentally friendly strategy for the synthesis of alkyl levulinates, bioproducts of relevance to the biorefinery industry, which can be applied as fragrances, flavoring agents, as well as fuel additives. [ABSTRACT FROM AUTHOR]

Porous carbon supported metal catalyst with embedded structure has witnessed the success in enhancing catalyst stability; however, the development of a simple yet efficient strategy to fabricate catalyst with controllable embedding degree is still a great challenge. Herein, we report a facile impregnation-coating-pyrolysis (ICP) strategy to fabricate ultrafine Ru nanoparticles embedded into N-doped porous carbon nanosheets (Ru@CN). Both the dispersion and exposure degree of Ru nanoparticles in Ru@CN catalyst could be efficient controlled through regulating the coating time of carbon precursors. As expected, the obtained Ru@CN catalyst exhibited an acid resistance for the hydrogenation of levulinic acid in an aqueous phase. Specifically, the spent Ru@CN catalyst shows a significant enhancement in catalytic activity compared with fresh one because the fact that part of Ru active sites confined inside carbon support could be liberated during the reaction process. We anticipate that this ICP strategy may provide a new approach to fabricate the embedded catalyst with high hydrothermal stability. [ABSTRACT FROM AUTHOR]

This study explores the esterification of levulinic acid with 1-pentanol, employing Dowex® 50WX8 as a catalyst under microwave irradiation. Key parameters such as the pentanol/acid molar ratio, temperature, and catalyst loading were evaluated and utilized for kinetic modeling. The kinetic behavior of the reaction was investigated using a dual-model approach: a pseudo-homogeneous model to account for the microwave effect and catalytic contributions modeled through LHHW and Eley–Rideal mechanisms. The best model was chosen based on statistical results obtained from Markov Chain Monte Carlo (MCMC) analysis, which involved an LHHW model with the surface reaction as the limiting step, resulting in an activation energy of 50.6 kJ mol−1 for the catalytic synthesis of pentyl levulinate. The role of the alcohol in the esterification route was explained, and catalytic stability was confirmed, with the catalyst maintaining activity over multiple cycles. The absence of mass transfer limitations was proved using the Weisz–Prater criterion. A plausible reaction pathway was proposed for the levulinic acid esterification over the 50WX8 catalyst. [ABSTRACT FROM AUTHOR]

The reductive amination of levulinic and 2‐acetyl benzoic acids with hydrogen and various amines proceeds efficiently in the presence of a homogeneous Ni/triphos‐catalyst. The reaction rate of the overall process is significantly enhanced using 3,3,3‐trifluoroethanol (TFE) as solvent. The optimized synthetic protocol allows for a straightforward access of >20 examples of N‐functionalized pyrrolidinones in high yields (75 % and >99 %). Upscaling to 10 mmol‐scale is demonstrated and mechanistic in situ studies revealed the presence of alkoxy‐ and hydroxylactams as crucial intermediates. [ABSTRACT FROM AUTHOR]

Multi‐metallic catalysts rely on the synergistic effect between metals to perform better catalytic effect in biomass hydrogenation experiments compared with mono‐metallic catalysts. A series of CuNiAl composite metal oxide catalysts promoted by silicotungstic acid (HSiW), which were prepared by co‐precipitation and impregnation methods, were characterized by powder X‐ray diffraction (XRD), N2‐physisorption, scanning electron microscope (SEM) and NH3 program temperature desorption (NH3‐TPD) and pyridine infrared adsorption (Py‐FTIR). Their catalytic performance was evaluated in the hydrogenation of levulinic acid (LA) to prepare γ‐valerolactone (GVL). The results showed that the addition of Cu could improve the hydrogenation activity of Ni, and the addition of HSiW could further increase the amount of acid sites in the catalysts. Both of them could enhance the conversion of LA to some extent. CuNiAl‐5SiW, the par excellence catalyst, relied on the synergistic interactions between metals as well as the Brønsted and Lewis acid active sites to show efficient hydrogenation performance. The CuNiAl‐5SiW catalyst demonstrated 96.9 % conversion of LA and more than 99 % selectivity to GVL under 2 hours of reaction time, 180 °C of reaction temperature, 3.0 MPa of initial hydrogen pressure and solvent‐free conditions. [ABSTRACT FROM AUTHOR]

In this work, levulinic acid (LLA) was used as a new bio-based solvent for solvolysis liquefaction of wood under mild conditions (temperature 160 ± 5 °C and atmospheric pressure). The liquefaction of sugar maple (Acer saccharum Marsh.) wood at a high rate (up to 93%) was obtained under these conditions. The liquefied product was divided into water-insoluble (WILW) and water-soluble (LArF) fractions. LArFs were mixtures of low-molecular weight compounds including unreacted LLA and furfuryl alcohol, as shown by electrospray ionization-mass spectrometry (ESI–MS) analysis. WILW has shown a high acid number (205–211 mg KOH/g) and a low hydroxyl number (< 23 mg KOH/g), which is in contrast with the conventional hydroxylated liquefied products reported in the literature so far. WILW was cured with LArF, a glycerol-liquefied wood, hexamine, and methylene diphenyl diisocyanate for the preparation of wood coatings. Cured coatings showed good pull-off adhesion strengths to the surface of beech wood, resistance to water, and low ΔE* color change when exposed to ultra-violet (UV) light. Liquefying wood in LLA provides a reactive product containing carboxylic acid groups that could be used to produce cleaner, petroleum-free materials. [ABSTRACT FROM AUTHOR]

Levulinic acid, a hydrolysis product of lignocellulose, can be metabolized into important compounds in the field of medicine and pesticides by engineered strains of Saccharomyces cerevisiae. Levulinic acid, as an intermediate product widely found in the conversion process of lignocellulosic biomass, has multiple applications. However, its toxicity to Saccharomyces cerevisiae reduces its conversion effciency, so screening Saccharomyces cerevisiae genes that can tolerate levulinic acid becomes the key. By creating a whole-genome knockout library and bioinformatics analysis, this study used the phenotypic characteristics of cells as the basis for screening and found the HMX1 gene that is highly sensitive to levulinic acid in the oxidative stress pathway. After knocking out HMX1 and treating with levulinic acid, the omics data of the strain revealed that multiple affected pathways, especially the expression of 14 genes related to the cell wall and membrane system, were significantly downregulated. The levels of acetyl-CoA and riboflavin decreased by 1.02-fold and 1.44-fold, respectively, while the content of pantothenic acid increased. These findings indicate that the cell wall-membrane system, as well as the metabolism of acetyl-CoA and riboflavin, are important in improving the resistance of Saccharomyces cerevisiae to levulinic acid. They provide theoretical support for enhancing the tolerance of microorganisms to levulinic acid, which is significant for optimizing the conversion process of lignocellulosic biomass to levulinic acid. [ABSTRACT FROM AUTHOR]

It has been shown that the nature of the metal precursor and the thermal effects during calcination determine the physicochemical properties of the catalysts and their catalytic activity in the levulinic acid (LA) and 5-hydroxymethylfurfural (HMF) hydrogenation reactions. The endothermic effect during calcination of the inorganic nickel precursor promoted higher metal dispersion and stronger interaction with the alumina surface. In contrast, the exothermic effects during the calcination of organic nickel precursors resulted in smaller metal dispersion and lower interaction with the support surface. A clear relationship was found between the size of the metal crystallites and the yield of LA hydrogenation reaction. The smaller crystallites were more active in the LA hydrogenation reaction. In turn, the size of the metal particles and their nature of interaction with the surface of the alumina influence the hydrogenation pathways of the HMF. [ABSTRACT FROM AUTHOR]

This work examined the hydrothermal breakdown of biomass into platform chemicals, including acetic acid (AA), formic acid (FA), 5-hydroxy methyl furfural (5-HMF), and levulinic acid (LA). Chicory was selected as feedstock because of its high potential to produce valuable chemicals. Reactions were performed with BSA (benzenesulfonic acid) and LABSA (linear alkyl benzene sulfonic acid) as sulfonic acid catalysts. The studies were conducted with different catalyst concentrations (100, 300, and 600 mM) for 110 minutes at 200 °C with a biomass-tosolvent ratio of 1g/25 mL. The variation of product yield and composition on parameters such as time, sulfonic acid concentration, and type of catalyst were investigated. The maximum levulinic acid yields in wt.% achieved through the experiments of this study were 22.65 wt.% (9.05 g/L) for 600 mM BSA and 85.93 wt.% (34.37 g/L) for 600 mM LABSA at 200 °C. [ABSTRACT FROM AUTHOR]

Levulinic acid (LA) and its valuable derivatives are in great demand in various applications. LA manufacturing from renewable resources through biorefinery processes has gained significant attention in sustainable LA production. However, the primary challenge in biorefinery is the separation of LA from other biomass products. The current review discussed the importance of the LA, its synthesis route, and the advantages and drawbacks of various LA separation and extraction methods. The application of adsorption, electrodialysis, crystallization, liquid–liquid extraction, and liquid membrane for LA extraction was elaborated. The potential of the liquid membrane technology, which can remove and recover desired products in a single step with high selectivity, was highlighted for the LA extraction. The advancement of various separation techniques used for LA extraction is required to fulfil the growing demand for LA products. [ABSTRACT FROM AUTHOR]

In a bid to explore the on-site biorefinery approach for conversion of forestry residues, lignocellulosic biomass into value-added products was studied. The bark white pine wood was subjected to the microwave technique of fast and slow hydrolysis under varying acid and biomass concentrations to produce levulinic acid (LA). The HCl (2% v/v) and plant biomass (1% w/v) were identified as the optimum conditions for fast wood hydrolysis (270 ºC for 12 sec), which led to maximum LA yield of 446.68 g/kg PB. The proposed sustainable approach is mild, quick, and utilized a very low concentration of the HCl for the production of LA. The hydrolysate was used as a medium for Kluyveromyces marxianus growth to produce 2-phenylethanol (2-PE). K. marxianus used 74–95% of furfural from hydrolysate as a co-substrate to grow. The proposed model of the integrated biorefinery is an affordable on-site approach of using forest waste into localized solutions to produce LA and 2-PE. [Display omitted] • Levulinic acid was produced using microwave-based hydrolysis of pine wood. • 2% HCl resulted in maximum levulinic acid production of 446.48 g/kg. • Kluyveromyces marxianus was able to grow on pine wood hydrolysate and produce 2-phenylethanol. • K. marxianus consumed 74–90% of furfural as co-substrate. • Pine wood can be an alternative option for Levulinic acid and 2-phenylethanol production. [ABSTRACT FROM AUTHOR]

Among the different polyoxometalate compounds, Keggin heteropolyacids have been extensively used as catalysts in several acid-catalyzed reactions, due to their strong strength of Bronsted acidity. These metal–oxygen clusters have a highly versatile structure that allows their conversion to derivatives, which are catalysts that are much more efficient than their precursors, with a greater catalytic activity in a plethora of reactions of industrial interest. Particularly, due to the inevitable exhaustion of fossil sources, reactions to valorize biomass have attracted significant attention, since it is a precious renewable raw material that can provide fine chemicals or fuels, minimizing our dependence on petroproducts. Biorefinery processes can produce platform molecules to achieve this goal. In this review, the recent advances achieved in the development of routes to converting biomass feedstocks to levulinic acid and furfural, which are valuable ingredients in biorefinery processes, using Keggin heteropolyacid catalysts were assessed. [ABSTRACT FROM AUTHOR]

Alkyl levulinate is a biomass-based chemical compound used as a fuel additive. This research aims to produce ethyl levulinate from levulinic acid and ethanol using esterification with the assistance of a heterogeneous sulfonated carbon catalyst. The carbon sulfonate catalyst is obtained from corncob waste that has undergone carbonization at 300 °C and sulfonation using sulfuric acid at a temperature of 150 °C for 8 h. The catalyst is used for esterification with predetermined operating variables using Box-Behnken Design (BBD) on the response surface methodology (RSM). The result shows significant variables for ethyl levulinate esterification are catalyst loading and esterification time. The FTIR analysis indicates the presence of S=O bonds in the sulfonated carbon catalyst. The XRD and SEM analysis shows that the sulfonated carbon catalyst is in amorphous and mesoporous form. Catalyst reusability demonstrates that the corncob-derived carbon sulfonate catalyst can be used up to 3 times. The optimum condition for esterification is 9 h of reaction, 10 % catalyst loading, and a molar ratio of levulinic acid to ethanol of 1:10, which has 83.15 % conversion. These results present the optimum parameter conditions for an efficient heterogeneous catalyst from corncob for producing ethyl levulinate.

We evaluated CO2 equivalent (CO2eq) greenhouse gas (GHG) emissions and minimum selling price of levulinic acid (LA) produced in two biomass-waste-based processes: the AlCl3/choline chloride (ChCl) process, and the formic acid (FA) process, with catalysts recycling. Six scenarios were synthesized to compare the performances of the two processes in Japan and Canada. In the AlCl3/ChCl process, the total GHG emission was 11.35–11.56 kg-CO2eq/kg-LA and those from the energy input to the pretreatment and ChCl production were 5.22 and 3.90 kg-CO2eq/kg-LA, respectively. In the FA process, the total GHG emission was 9.46–9.68 and 22.29–22.51 kg-CO2eq/kg-LA for 60 wt% and 80 wt% FA, respectively. The operational emissions for makeup FA input were 7.65 and 20.80 kg-CO2eq/kg-LA (60 wt% and 80 wt%, respectively), which accounted for more than 80% in all scenarios. The optimization of the product purge volume, FA concentration in the pretreatment, and FA production using biomass and/or renewable energy are critical parameters to reduce overall environmental impacts of the processes. The liquid content of the solid residue (moisture, water soluble organic matters, and catalyst) had insignificant influences on the GHG emission and minimum selling price. In the FA process, combustion of solid residue can compensate the GHG emissions from the reaction and separation units.

This study investigates the process of isolating and characterizing cellulose from Oil Palm Empty Fruit Bunch (OPEFB) fibers collected from Sime Darby Plantation, Selangor. The OPEFB fibers underwent a sequence of chemical processes including dewaxing, alkali pretreatment and bleaching, to isolate the cellulose. The resulting cellulose was analyzed for its composition, crystallinity and yield of hydrolysis products. Comparative analysis with recent studies indicates that the cellulose content of the isolated fibers falls within the reported range, with relatively lower lignin content suggesting a successful lignin removal during chemical treatments. The crystallinity index of the cellulose significantly increased after the post-treatment, reaching 76.43%, which is higher than some reported values. The hydrolysis of the isolated cellulose from OPEFB yielded levulinic acid (LA) levels comparable to commercial cellulose, with the OPEFB-based cellulose producing an LA yield of 8.98% lower than the 9.73% from commercial cellulose. This study highlights the potential of OPEFB as a viable source of high-quality cellulose for the production of sugars and LA.

γ‐Valerolactone (GVL) can be obtained by efficient hydrogenation of levulinic acid using ruthenium‐based catalysts in an aqueous medium. This paper reports an in‐depth study on the activity and selectivity of Ru catalysts supported on zirconia‐alumina, focusing on the effect of Ru concentration (0.5, 1.5 and 3 wt. % of Ru) and the selection of operational reaction variables. The results showed that the activity strongly depends on the number and oxidation state of the supported ruthenium particles. The most active catalyst, Ru3/ZA, presented the highest number of nanometric particles of zerovalent Ru and the highest number of acid sites. This catalyst gave ca. 100 % selectivity towards GVL, at high conversion of levulinic acid (over 99 %) under the best operating conditions evaluated (120 °C, 3 MPa H2 pressure, 1 h of reaction, and 0.1 g of catalyst). In addition, this catalyst kept high levels of conversion and selectivity after successive reuse cycles. [ABSTRACT FROM AUTHOR]

The selective conversion of levulinic acid (LA) obtained from lignocellulosic biomass represents a crucial pathway for producing the key value‐added chemical compound γ‐valerolactone (GVL). Herein, we constructed a series of Pt‐based titanium‐silicalite‐1 (TS‐1) bifunctional catalysts modified with rare earth metal Ce through a simple spin‐coating impregnation method, and the catalytic performance was significantly improved compared to the unmodified Pt1.2/TS‐1. Pt0.7‐Ce0.5/TS‐1 exhibited the best aqueous‐phase catalytic activity (with a GVL yield of 99.4%). The introduction of CeOx can reduce the particle size of Pt nanoparticles and promote the formation of electron‐rich Pt species while delivering abundant oxygen vacancies (OV) for the catalysts. The characterization and testing results highlight the synergistic effect of OV and electron‐rich Pt sites on the oriented adsorption and selective hydrogenation of LA, providing new insights into constructing more efficient noble metal‐based zeolite catalysts for biomass conversion. [ABSTRACT FROM AUTHOR]

The self-condensation of levulinic acid was studied using cesium silicotungstate (CsxH4-xSiW12O40) catalyst without solvent. The CsxH4-xSiW12O40 catalyst was characterized by FT-IR, Raman, XRD, NH3-TPD, N2 adsorption–desorption, SEM, and ICP. The results showed that the structure of Keggin was well retained in all samples of CsxH4-xSiW12O40 catalyst. With a decrease of Cs content, the acid strength of CsxH4-xSiW12O40 catalyst decreased, and thus the yield of cyclic C10 products decreased accordingly, while that of linear C10 products increased. The effect of reaction conditions on levulinic acid self-condensation was studied using Cs2.5H1.5SiW12O40 (H2SO4) catalyst. Under the conditions of catalyst amount of 15 wt.%, reaction temperature of 130 °C, and reaction time of 6 h, the conversion of levulinic acid was 53.8%, and the total selectivity of C10 products were 83.1%. Through spectroscopic characterization and DFT calculation, the possible structures of C10 products of levulinic acid aldol self-condensation were deduced. The results showed that levulinic acid condensed in two different paths to form two intermediates, 4-hydroxy-4-methyl-6-oxononanedioic acid and 3-acetyl-4-hydroxy-4-methylheptanedioic acid. The two intermediates were then subjected, respectively, to lactonization and intramolecular dehydration to three cyclic C10 products: 5-(2-methyl-5-oxotetrahydrofuran-2-yl)-4-oxopentanoic acid, 3-(2-methyl-5-oxotetrahydrofuran-2-yl)-4-oxopentanoic acid, and 3-(3-acetyl-2-methyl-5-oxotetrahydrofuran-2-yl) propanoic acid, and to obtain the linear C10 product, (E)-4-methyl-6-oxonon-4-enedioic acid. [ABSTRACT FROM AUTHOR]

Covalently bonded sulfamic acid on the titanate nanotubes (TNTs-N(SO3H)-(CH2)2-NHSO3H) was designed and successfully fabricated by the post-synthesis modification method. The as-prepared catalyst was characterized by a variety of characterization techniques such as FT-IR, TEM, XRD, XPS, and TG-DTG. The catalytic activity of TNTs-N(SO3H)-(CH2)2-NHSO3H was evaluated for the synthesis of n-butyl levulinate (BL) from levulinic acid (LA). It was found that the tube-like structure of the TNTs still maintained during the modification process, and Brønsted and Lewis acid sites can be efficiently immobilized on the TNTs. The effects of reaction factors such as reaction time, reaction temperature, and catalyst dosage on the esterification of LA were systematically studied. Under the optimal reaction conditions, a relatively high yield of BL (95.3%) was achieved for esterification of levulinic acid owing to the strong Brønsted acidic sites. Furthermore, the hybrid catalyst TNTs-N(SO3H)-(CH2)2-NHSO3H was used at least five times without significant decrease in activity, and no leaching of the active species in hot filtration test was observed. [ABSTRACT FROM AUTHOR]

Bimetallic NiCu catalysts supported on mesoporous SiO2 nanorods were prepared by impregnation method with the help of complexing agents. The introduction of various complexing agents including citric acid (CA), polyvinyl pyrrolidone (PVP), triethanolamine (TEOA), triethylamine (TEA) and ammonia (AMH) significantly affected the metal particle size, surface chemical state, redox and acidic properties. The NiCu/SiO2–PVP catalyst had the smallest metal nanoparticle sizes of 2.3 nm among the catalysts. The variation of metal particle size resulted in the differences of the metal-support interaction, which further caused the changes of the redox property. Acidic property was another indispensable factor to promote this reaction, and the types of complexing agents did not change the acidic strength distribution but the total number of that. The apparent activation energy on NiCu/SiO2–PVP was 26.55 kJ/mol, which was obviously lower than that on NiCu/SiO2–AMH (37.49 kJ/mol). Consequently, the NiCu/SiO2–PVP catalyst exhibited the best activity compared to other catalysts in the gas phase catalytic hydrogenation of levulinic acid with formic acid as the hydrogen source, achieving the highest levulinic acid conversion of 76.9% and γ-valerolactone selectivity of 91.6%. It also showed good catalytic stability within 20 h time-on-stream. [ABSTRACT FROM AUTHOR]

In the process of converting biomass into high value-added chemicals, transfer hydrogenation as a mild hydrogenation method has attracted more and more attention. The catalysts with hydrogenation sites (nano CuNi alloy) and acid sites (Al oxide) highly dispersed on the surface of a stable support (active carbon) were prepared and the importance of acid sites for the activity of CuNi catalysts in transfer hydrogenation was demonstrated. The catalysts showed promising catalytic activity on the transfer hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL). The CuNi-1Al/AC with 5 wt.% CuNi alloy and 5 wt.% Al got 97.2% GVL yield and 100% LA conversion at 220 ℃ in isopropanol for 2 h. The high activity of the catalyst is attributed to the promoted esterification by the supported acid sites. The Al-modified catalyst also showed activity for esterification reaction in different alcohol hydrogen donors. The catalyst occurs inactive during the cycle due to the shedding of the active components, and the stability of catalyst is effectively improved by a stepwise impregnation. [ABSTRACT FROM AUTHOR]

Levulinic acid (LA) is a worthwhile biochemical usable as a building-block for the formation of wide variety of chemicals and fuels. In the present work, a series of ion-exchanged ZSM-5-type zeolites were formulated in order to obtain a bifunctional catalyst with modulated acidity in the aspect of amount, strength, and type (Lewis and Brønsted) for the transformation of glucose as a bio-based model component to LA. In particular, ion-exchanged ZSM-5 were prepared by an aqueous ion-exchange method using NH4Cl and CuCl2 salts and a microwave-assisted solid-state ion-exchange technique using solid transition metal (Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(II)) chlorides. Morphological features and acidity of the catalysts were assessed using XRD, SEM, EDX, TG–DTA, N2-physisorption, NH3-TPD, and FTIR both as such and by adsorbing/desorbing 2,6-dimethylpyridine (2,6-DMP) as a probe molecule. Microwave has been selected as the best ion-exchange technique which led to the improvement of Lewis acidity of ZSM-5 and obtaining a balanced acid catalyst with a high Lewis to Brønsted acid ratio (L/B) and mostly weak and medium acid sites. Among several metal ions used for ion-exchange process, Cu(II) with high charge transfer and by introduction of low amount of acid sites acted as the best option for desired reaction pathway. Therefore, CuZSM5-M prepared by microwave technique with a balanced L/B ratio has shown the best performance in the conversion of glucose to LA with 37% yield. [ABSTRACT FROM AUTHOR]

BACKGROUND: Levulinic acid is an important platform chemical derivable from lignocellulosic biomass. In this work, the hydrogenolysis of levulinic acid to produce 1,4‐pentanediol was performed over some Co‐based non‐noble catalysts. The relationship between the catalyst properties and the catalytic activity was investigated, and the effects of the reaction conditions on the catalytic activity were studied. RESULTS: The Co/ZrO2 catalyst prepared by a coprecipitation method showed a high catalytic performance in the hydrogenolysis of levulinic acid to form 1,4‐pentanediol. The calcination of Co/ZrO2 significantly affected the catalytic activity, and a high calcination temperature of 750 °C could promote the formation of 1,4‐pentanediol. Meanwhile, the reduction of Co/ZrO2 at 400 °C in an H2 flow was beneficial for producing 1,4‐pentanediol, and the Co species after the reduction existed as the forms of Co2+ and Co0. A high H2 pressure and a moderate reaction temperature of 200 °C were beneficial for producing 1,4‐pentanediol, and a high 1,4‐pentanediol selectivity of 85.6% with a complete conversion of levulinic acid was obtained over the Co/ZrO2 catalyst at 200 °C under an H2 pressure of 7 MPa. CONCLUSION: The Co species in the 400 °C‐reduced Co/ZrO2 catalyst existed as the forms of Co2+ and Co0. It was proposed that the synergistic effect of Co2+ and Co0 contributed to the effective formation of 1,4‐pentanediol from levulinic acid. © 2024 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Levulinic acid is a useful chemical platform derived from lignocellulose, which is applied in many applications such as solvents, fuels and pharmaceuticals. The natural structure of lignocellulose is recalcitrant to access cellulose and upgrade to levulinic acid. Here we showed that a combination of rice straw dissolution in carboxylic acid-based deep eutectic solvent (DES) and acid hydrolysis enabled rice straw conversion into levulinic acid. Among carboxylic acid-based DESs (choline chloride-acetic acid, choline chloride-oxalic acid, choline chloride-malonic acid and choline chloride-succinic acid), choline chloride-Oxalic acid DES potentially dissolved rice straw (100 °C for 2 h) and converted the dissolved cellulose to levulinic acid (52%) by HCl at mild condition (120 °C at 10 h and atmospheric pressure). Our approach is superior to conventional processes for levulinic acid production, such as no separation of intermediates (glucose and HMF), mild condition and inexpensive DES cost, making the one-pot process efficient and economically. [ABSTRACT FROM AUTHOR]

The aim of the present work is to investigate an environmentally benign method for the catalytic conversion of biomass derived compounds into fine chemicals. Levulinic acid (LA) is one of the key biomass-derived chemicals that can be converted into biofuels and various other value-added chemicals. n -Butyl levulinate ester is an important chemical used in the production of fuel additives, solvents, plasticizing agents, and odorous substances. The work presented here focused on the esterification of n-butyl levulinate by reaction of LA and n-butanol in the presence of synthesized 20% tungstophosphoric acid (TPA) supported zeolite β (TPA-Zβ), CsTPA-Zβ and Cs-Zβ catalysts. Various catalyst characterization techniques have been used, specifically, XRD, SEM–EDS, FT-IR, nitrogen physisorption and NH3 -TPD. The highest % yield of n -butyl levulinate is obtained with shorter reaction time in the case of a 20% TPA supported zeolite β catalyst, calcined at 300 °C. The addition of Cs ions to TPA appears to improve catalytic performance. [ABSTRACT FROM AUTHOR]

Background: Butyl levulinate (BL) was produced by the esterification of levulinic acid (LA) and n‐butanol (BOH) using a sulfonated nanocomposite of titania–zirconia as catalyst. A full factorial design was employed for studying the effects of reaction time, mole ratio and catalyst loading on LA conversion. Results: The synthesised catalyst was subjected to various characterisation techniques such as X‐ray diffraction, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller measurements, thermogravimetric analysis, temperature‐programmed desorption and scanning electron microscopy–energy dispersive X‐ray analysis indicating the presence of a nanocrystalline structure with good surface area and good stability at the operating temperature. The experimental data were analysed using the response surface method, and a complete quadratic regression model was built. The LA conversion was 85.37% for the optimised reaction conditions of 1:7 mole ratio, a catalyst loading of 1 wt% and a reaction time of 5 h at 110 °C. Based on the Langmuir–Hinshelwood–Hougen–Watson model, a kinetic model was developed. The activation energy was found to be 20.4 ± 0.8 kJ mol−1 from an Arrhenius plot. Reusability and leaching results are also reported. Conclusion: The catalyst exhibited good reusability and stability. Sulfonated TiO2–ZrO2 used to catalyse the reaction between LA and BOH to produce BL has proved to be a good candidate as a green catalyst. The results presented play an important part in directing subsequent research and commercialisation activities aimed at valorising LA to fuel additive. © 2023 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

A novel nano-photocatalyst has been prepared using hydroxyapatite (HAp) derived from waste fish scale and fly ash-derived aluminosilicate (SiO2-Al2O3) grafted with zirconium oxide (ZrO2) active sites by innovative photo-hydrothermal protocol. The physiochemical properties of the prepared photocatalyst have been characterized by different analyses like TGA, XRD, FTIR, XPS, UV–VIS–NIR, BET, NH3-TPD, HRTEM, and DLS. The optimal catalyst has a zirconium loading of 20 wt% and has a low bandgap energy of 2.15 eV as confirmed by UV–VIS–NIR spectroscopy. The optimal catalyst also depicted a high acidity of 1.52 mmol NH3/g and a specific surface area of 62.872 m²/g. Owing to the high acidity, specific surface area, and low band gap energy the photocatalyst has led to achieving an elevated yield of 76.6% levulinic acid (LA) from glucose in hybrid irradiation reactor (HIR) deploying UV and FIR radiations at appreciably low temperature and reaction time of 115 ℃ and 2 h respectively. Under the same reaction conditions, the conventionally heated reactor (CHR) gave a very low yield of 23.7%. Individual radiation effects on LA yield evinced the synergistic advantageous effect of the hybrid irradiation technique. The catalyst reusability and regenerative study confirmed the high stability of the prepared catalyst. Also, a comparative LCA study has been conducted between HIR and CHR systems which revealed that HIR was more environmentally sustainable than CHR. HIR -based process demonstrated a reduction in 59% global warming potential, 70.66% forest resource scarcity, and 65% lower terrestrial ecotoxicity while being 120% more energy efficient than CHR-based reaction making HIR more environmentally sustainable as well as economically feasible.

The conversion of levulinic acid (LA) into alkyl levulinates is highly significant due to the wide range of applications for these products, including their use as fuel additives, solvents, and fragrances. In order to meet the growing need for environmentally friendly chemical production, this study takes a circular economy approach by upcycling a common urban waste, i.e., pine needles, to synthesize a robust heterogeneous acid catalyst, subsequently used to efficiently upgrade LA into levulinates. By utilizing a single-step procedure under mild operating conditions, the resulting PiNe–SO3H catalyst demonstrated good performances and flexibility in synthesizing diverse bio-derived levulinates. In fact, the catalyst showed an exceptionally broad range of applicability, resulting in isolated yields ranging from ̴ 46% to ̴ 93%, which is an unprecedented achievement. The catalyst's ability to be reused was tested, revealing remarkable performance for up to 10 consecutive cycles with negligible loss in efficiency. Additionally, a significant focus was directed towards developing a method that minimizes waste during the isolation process. This involved optimizing reaction conditions and rationalizing work-up procedures, resulting in low Environmental factor (E-factor) values ranging from 1.2 to 8.9. To comprehensively assess the overall environmental sustainability of the process, various additional green metrics were calculated, and the Ecoscale tool was employed as well. Furthermore, mechanistic investigations elucidated the favored reaction pathway, underscoring that, under the optimized conditions, the prevailing mechanism entails direct esterification, as opposed to the generation of a pseudo-ester intermediate.

Supported bimetallic ruthenium-tin (denoted as Ru-Sn(x); x = molar ratio of Ru/Sn) catalysts were examined for room temperature (RT) hydrogenation of biogenic platform chemicals of levulinic acid (LA) to g-valerolactone (GVL). Six types of metal oxide support c.a. Nb2O5, TiO2, ZnO, ZrO2, g-Al2O3, active charcoal (AC), were employed as the support for Ru-Sn(x). Ru-Sn(3.0)/Nb2O5 (Ru/Sn = 3.0) that reduced at 500 oC demonstrated the highest yield of GVL (98%) at 30 oC, 30 bar H2 for 3 h. The increase in Sn loading amount (Ru/Sn = 1.5) resulted in decreasing of LA conversion (83%) under the same reaction conditions. Among the studied supported Ru-Sn catalysts, Nb2O5 and ZnO supports exhibited better catalytic performances than that other for RT hydrogenation of LA and various biogenic platform chemicals. The Ru-Sn(3.0)/Nb2O5 catalyst was characterized by means of various adsorption and spectroscopic techniques. The Ru-Sn(3.0)/Nb2O5 catalyst was found to be reusable without any significant loss of its activity. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).